Introduction.--Mendel, G. Experiments in plant- hybridisation [tr. of a paper originally published in the Verhandl. Naturf. ver. in Brünn, 1866]--Mendel, G. On Hieracium-hybrids obtained by artificial fertilisation [tr. of a paper originally published in the Verhandl. Naturf. ver. in Brünn, 1870]--A defence of Mendel's principles of heredity [against the criticism of W. F. R. Weldon]